JPH10167007A - Seat belt retracter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To fit a seat belt on an occupant without looseness and to sufficiently reduce oppressive sensation against the occupant by controlling energizing force by moving a movable member by a supersonic wave motor so that the energizing force becomes a target value. SOLUTION: Drawing quantity of a seat belt is detected as rotational quantity of a reel 20 by a rotary encoder 107. When a tong is installed on a buckle and a buckle switch is switched on, a supersonic wave motor 24 rotates a spring case 34 by specified times in the winding-up direction of a spring 32, and winding force of the spring 32 is improved. Consequently, looseness of the seat belt is removed, and the seat belt is closely fitted to an occupant. As oppressive sensation to the occupant is strong as it is, the spring case 34 is rotated in the loosening direction of the spring 32 by specified times. Accordingly, the oppressive sensation of the seat belt is reduced or eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a retractor for a seat belt device provided in a vehicle for protecting an occupant. More specifically, the present invention relates to a seat belt configured such that the seat belt softly contacts the occupant when the occupant wears the seat belt, and the seat belt is strongly wound up when the seat belt is stored in the retractor. Regarding the retractor.

[0002]

2. Description of the Related Art As is well known, a seat belt device unwinds a seat belt from a reel of a retractor provided in a vehicle, locks the seat belt to a buckle by a tongue, and thereby restrains an occupant to a seat. It was made.

[0003] In this seatbelt device, the seatbelt unwound from the retractor always receives tension in the winding direction from the retractor, and is configured to fit an occupant.

However, since the seat belt is constantly in contact with the occupant's body as described above, if the tension is too large, the pressing force applied to the occupant increases, which causes discomfort. Conversely, if the tension is small, the retracting force at the time of winding (retracting) into the retractor becomes weak, and the winding of the seat belt becomes slow.

In order to satisfy such a conflicting demand, Japanese Utility Model Publication No. 57-20212 discloses that a rotatable spring case is connected to a winding shaft of a seat belt via a spiral spring (spiral spring). A seat belt in which teeth engraved on a peripheral surface of a spring case are meshed with a manually operated adjustment gear, and the spring case is rotated by the adjustment gear to adjust a winding spring force of a mainspring spring. Winding devices have been proposed.

However, Japanese Utility Model Publication No. 57-2021
In the No. 2 retractor, since the urging force of the mainspring is manually adjusted, it is difficult to adjust the strength of the seat belt retracting force. It is not possible to sufficiently satisfy the contradictory required characteristics of securing the pulling force at the time.

Japanese Utility Model Publication No. 63-5965 discloses a seat belt in which a spring case surrounding a mainspring for urging a reel in a seatbelt rewinding direction is rotated by a motor, thereby adjusting a winding mounting force of the mainspring. A retractor is described. In the publication, when the tongue is mounted on the buckle, the spring case is rotated to the side where the spring is loosened, thereby reducing the tension of the seat belt.
When the tongue is released from the buckle, the spring case is rotated in the spring tightening direction, whereby the seat belt is wound up by the retractor with a strong urging force.

In Japanese Patent Application Laid-Open No. Hei 5-24507, a mainspring for urging a reel shaft in a seat belt winding direction is connected to the other end of the mainspring, and a seat is wound by partially winding the mainspring. A seat belt retractor having a winding force adjusting device for adjusting a belt winding force, wherein a seat belt retractor in which at least two first and second spring springs having different spring constants are connected as the mainspring spring. Is described.

In the seat belt retractor disclosed in Japanese Patent Application Laid-Open No. H5-24507, a plurality of mainsprings having different spring constants are connected in series. When the winding device is partially wound by the adjusting device, the mainspring spring having the smaller spring constant is selectively wound by the winding force adjusting device, and the urging force of the reel shaft by the spring spring array becomes extremely strong. As a result, it is possible to wind the seat belt strongly and quickly.

[0010] When the mainspring with a small spring constant is unwound from the winding force adjusting device, the spring spring array as a whole has a considerably small spring constant, and the winding force applied to the reel shaft is considerably small. Become.
As a result, the seat belt fits the vehicle occupant with a very small force, and the occupant's feeling of oppression is eliminated.

[0011]

[Problems to be Solved by the Invention] Japanese Utility Model Publication No. 63-5965
In the seat belt retractor disclosed in Japanese Patent Application Laid-Open Publication No. H11-139, the urging force of the mainspring is large until the tongue is attached to the buckle, and a large force is required to pull out the seat belt stored in the retractor. In addition, when the tongue is attached to the buckle, the urging force becomes small immediately, and the seat belt cannot be fitted to the occupant without loosening.

Japanese Patent Application Laid-Open No. Hei 5-24507 does not disclose a structure for fitting a seat belt to a passenger without loosening while reducing the feeling of pressure on the passenger.

The present invention has been made in view of such a conventional example, and provides a seat belt retractor capable of fitting a seat belt to an occupant without loosening and having a sufficiently small pressure on the occupant. It is intended for.

[0014]

According to the present invention, there is provided a seat belt retractor comprising: a reel for winding a seat belt;
One end is connected to the reel, a spiral spring for urging the reel in the seat belt winding direction is connected to the other end of the spring, and a direction in which the urging force of the spring is changed. A movable member, an ultrasonic motor that changes the biasing force by moving the movable member, a biasing force detecting unit that detects a biasing force generated by the spring, and a biasing force detected by the biasing force detecting unit. Urging force control means for controlling the urging force by moving the movable member by the ultrasonic motor so as to attain a target value.

In such a seat belt retractor, the urging force of the spring is detected, and the urging force is controlled so that the urging force becomes a target value. Therefore, the seat belt is fitted to the occupant without slack, and the seat belt is compressed. The feeling can be made sufficiently small.

In the present invention, tongs may be provided a tongue engagement detecting means for detecting that engaged with the buckle, the biasing force of the spring when the seat belt storage and T _1, after the seat belt withdrawing, tongue buckle the biasing force of the spring until it engages with the smaller T ₂ than T _1, after the tongue is engaged with the buckle, once the urging force of the spring and higher T ₃ than T _2, then, the biasing force and lower T ₄ than T _3, when the tongue becomes disengaged with respect to the buckle, the sheet to the belt storage completion, preferably the urging force and high T ₅ than either T ₁ and T _3.

Further, in the present invention, the reel is arranged such that the axis of the reel is perpendicular to the side wall with respect to a frame having a pair of parallel side walls and a connecting portion connecting the side walls. An emergency lock mechanism for a seat belt retractor is provided on a first reel shaft which is supported in the same direction and protrudes from an axial position of one end face of the reel. A rotation amount detecting means is connected, and the spring is wound around the outer periphery of a second reel shaft protruding from the axis position of the other end face of the reel. A case shaft protrudes coaxially outside the frame, and the case shaft is located at the rotor axis position of the ultrasonic motor disposed outside the spring case. Fitted shaft hole is provided with, it is preferable that the casing rotation amount detection means disposed on the outside of the ultrasonic motor is connected to the distal end of the casing shaft.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 to 3 are exploded perspective views of a seat belt retractor according to an embodiment of the present invention.
FIG. 4 is a sectional view of the seat belt retractor, FIG. 5 is a spring characteristic diagram of the spring, and FIG. 6 is a control block diagram. FIG. 2 is an enlarged view of the lock mechanism shown in FIG.

The frame 10 includes a pair of parallel side walls 12,
14 and a back plate portion 16 connecting these side wall portions 12 and 14 to each other.
And In this frame 10, the seat belt 1
A reel 20 for winding the reel 8 is provided. The reel 20 is inserted into the openings 12a and 14a of the side wall portions 12 and 14.

An emergency lock mechanism 22 for the reel 20 is provided outside the side wall portion 14. The side wall 12
A spring mechanism 26 for urging the reel 20 in the seat belt rewinding direction is provided on the outside, and an ultrasonic motor 24 for adjusting the urging force is provided on the outside.

Next, the structure of the spring mechanism 26 will be described.

The spring mechanism 26 includes a spring 32 for urging the reel 20 in the seat belt winding direction, a housing 33 surrounding the spring 32, and a spring case 34. The spring 32 is formed of a spiral spring. The center end of the spring 32 is connected to the bush 3 with respect to the second reel shaft 31 (FIG. 4).
5, and the outer peripheral end is locked by a hook portion 34 a on the inner peripheral surface of the spring case 34. In addition, the reel shaft 31 protrudes in the axial direction from the axial portion of the end surface of the reel 20.

The housing 33 is provided on the side wall 1 of the frame 10.
2, the spring case 34 has its annular peripheral wall 34b slidably fitted in the housing 33.

A hexagonal case shaft 34 c projects coaxially with the reel 20 from the outer surface of the spring case 34. The case shaft 34c is inserted into a hexagonal shaft hole 36 penetrated by the rotor of the ultrasonic motor 24. The input shaft 37a of the rotary encoder 37 is engaged with the tip of the case shaft 34c.

The inner circumference 32a of the spring 32 has a larger spring constant than the outer circumference 32b.
Therefore, when the seat belt 18 is pulled out from the reel 20, the outer peripheral side 32b having a small spring constant is first tightened, and then the inner peripheral side 32a having a large spring constant is also tightened.

[0026] Incidentally, when the seat belt 18 is pulled out, the reel 20 is rotated in the arrow A ₁ direction, when winding the seat belt 18 rotates in the arrow A ₂ direction.

Next, the configuration of the lock mechanism 22 will be described.

A ratchet wheel 38 coaxial with the reel 20 is fixed to the other end of the reel 20. The reel shaft 40 passes through the ratchet wheel 38 and the reel shaft 40
It protrudes coaxially with zero. This reel shaft 40
At the base side is a large-diameter circular shaft portion 40a, and a square shaft portion 40b is formed adjacent to the circular shaft portion 40a. The circular shaft portion 40a has an opening 4 of a tie plate 42.
3 and the center hole 48 of the lock ring 44 are fitted.

The tie plate 42 supports one end of a C-shaped spring 50 described below. The opening 43 is provided on the tip side of the tie plate 42, and an opening 64 described later is provided on the other end side. The rear end of the tie plate 42 is supported by the frame side wall portion 14 by the shaft pin 60 inserted into the opening 64. That is, the tie plate 42 is provided between the projecting portion 40 and the shaft pin 60.

One end 50a of the C-shaped spring 50 is locked in a locking hole (spring hanger) 52 provided substantially in the center of the tie plate 42, and the other end is locked in a locking ring 44 (spring hanger). 54. The spring hanger 5 extends around the shaft 40.
A biasing force is applied to the lock ring 44 in the direction of the arrow A2 by the spring 50 provided between the _{second and the second} 54.

The lock ring 44 is provided with internal teeth 56.

The pawl 5 is provided on the side wall 14 of the frame 10.
8 has a shaft pin 60 inserted through its opening 58a.
It is pivoted by The tip of the pawl 58 can engage with teeth on the outer peripheral surface of the ratchet wheel 38. A protruding pin 62 protrudes from a middle portion of the pawl 58. As described above, the opening 64 on the tip side of the tie plate 42 is also fitted to the shaft pin 60. This shaft pin 60 is
It is attached to the hole 65 of the frame side wall portion 14.

The lock ring 44 is integrally provided with a projecting portion 66 projecting radially. This overhang 66
Wherein the pawl 58 is intended for turning in the C ₁ direction, the overhung portion 66, arcuate long hole 70 extending in the constant radius position with respect to the central hole 48 is provided, the length The protruding pin 62 of the pawl 58 is inserted into the hole 70.

The square shaft portion 40b of the reel shaft 40 which penetrates through the center hole 48 of the lock ring 44 and projects outside thereof
A central square hole 72a of the hook retainer 72 is fitted into the hook retainer 72. Protrusions 76 and 78 for supporting the hook 74 are provided on the periphery of the hook retainer 72 so as to face each other in the diametrical direction. A hook 74 is attached to the projections 76 and 78.
The hooks 74 are supported by the hook retainer 72 so as to be able to linearly reciprocate in the direction (B ₁ , B ₂ directions) connecting the projections 76, 78.

The spring locking portion 72b with the hook retainer 72 and the hook 74, between 74b are compression coil spring 84 is interposed, the hook 74 is biased in the arrow B ₁ direction. A hook 86 is provided at a part of the outer peripheral edge of the hook 74 so as to be able to engage with the internal teeth 56 of the lock ring 44. A connecting pin 88 is provided on the outer surface of the hook 74.

The hook 74 is, in the normal state, takes the position shifted in the arrow B ₁ direction by being biased in the compression coil spring 84, as a result, the pawl 86 is disengaged from the internal teeth 56 I have.

The connecting pin 88 is fitted with a locking hole 92 provided in the vicinity of the outer peripheral edge of the disk-shaped flywheel 90. A gear ring 96 having external teeth is fitted around the entire circumference of the flywheel 90. A bent end portion 98a of an arc-shaped spring 98 is mounted on a cutout portion 90a on the outer peripheral edge of the flywheel 90, and the spring 98 is slidably pressed against the inner peripheral surface of the gear ring 96. The gear ring 96 is slidable and rotatable while receiving a frictional force against the flywheel 90.

An acceleration sensor 100 having a lever 102 which engages with teeth on the outer peripheral surface of the gear ring 96 is mounted on the frame side wall portion 14. The acceleration sensor 100 has a tiltable weight 104 accommodated in a sensor case 103 and a lever 102 rotatably mounted on the upper part of the sensor case 103.

When an acceleration equal to or more than a predetermined value is applied to the weight 104, the weight 104 tilts, and the weight 10
The lever 102, which has overlapped with No. 4, is pushed upward,
The tip of the lever 102 engages with the gear ring 96. If the seat belt 18 is about to be pulled out in this state,
The rotation of the reel 20 is stopped as follows.

[0040] When the reel 20 attempts to rotate, the hook retainer 72 engaged with the square shaft portion 40a of the square of the reel 20 is rotated in A ₁ direction of the first and second views. At this time,
Projections 76 and 78 of the hook retainer 72 to rotate in the arrow A ₁ direction together with the hooks 74 also hook retainer 72 engaging the holes 80 and 82. However, the hook 74
The rotation of the flywheel 90 with which the pin 88 is engaged is stopped (that is, the flywheel 90 is stopped because the arcuate spring 98 is pressed against the stopped gear ring 96). the hook 74 can not rotate as it is, only the hook 74 min the hook retainer 72 is rotated in the a ₁ direction is slid in the arrow B ₂ direction, the pawl 86 is engaged with the internal teeth 56 of the lock ring 44 .

[0041] The results are to rotate in the arrow A ₁ direction to the lock ring 44 via the hook retainer 72 and the hook 74 is also dragged in rotation of the reel 20. Then, the projecting portion 66 of the lock ring 44 also rotates in the A ₁ direction, the pawl 58 having a pin 62 engaged with the long hole 70 of the overhung portion 66 is rotated in the arrow C ₁ direction. Thereby, the tip of the pawl 58 is engaged with the ratchet wheel 38 of the reel 20, the reel 20 is firmly locked, and the seat belt 18 is prevented from being pulled out.

The emergency lock mechanism 22 is
The cover 106 is covered with the frame side wall 1.
4 attached.

A rotary encoder 107 is provided outside the cover 106. The input shaft 107a of the rotary encoder 107 is engaged with a concave hole 40d at the tip of the reel shaft 40.

As shown in FIG. 4, the ultrasonic motor 24 includes a piezoelectric element array 110 and a piezoelectric element array 11 arranged in a circle.
Annular stator 112 installed in a state of being substantially in contact with zero
And a circular rotor 114 at the center of which is fitted with the case shaft 34c.

The rotor 114 is a disc-shaped annular spring 1.
The urging force of 16 presses the annular stator 112.

When the piezoelectric element array 110 is not energized, the circular rotor 114 is stopped by being strongly pressed by the spring 116 against the annular stator 112, and the case shaft 34 c is connected to the annular stator 112 via the circular rotor 114. Then, the rotation is stopped. That is, when the piezoelectric element row 110 is not energized, the spring case 34 cannot rotate.

When an ultrasonic signal is applied to the annular piezoelectric element array 110, the annular piezoelectric element array 110 is distorted in a wave shape in accordance with the ultrasonic signal, and the rotor 11
Rotate 4.

The amount of rotation of the spring case 34 accompanying the rotation of the rotor 114 is detected by the rotary encoder 37. This detection signal is output from the rotary encoder 10.
7, is input to the control unit 120 (FIG. 6). The signal of the buckle switch 122 is also input to the control unit 120. The control unit 120 controls the operation of the ultrasonic motor 24 based on these signals.

In the seat belt retractor thus configured, when the seat belt 18 is not pulled out, the spring case 34 is stopped at a position where the spring 32 is biased to such an extent that the seat belt 18 is not pulled out by its own weight. doing.

When the pull-out of the seat belt 18 is detected by the rotary encoder 107, the ultrasonic motor 2
4 rotates the spring 34 so as to weaken the spring force. This state where the spring force is weak is maintained until the seat belt 18 is pulled out from the seat belt retractor and the tongue is attached to the buckle.

Therefore, the vehicle occupant receives little resistance when pulling out the seat belt 18 from the seat belt retractor, and the seat belt 1
8 can be pulled out.

At this time, the amount of pulling out of the seat belt 18 is determined by the rotary encoder 107 on the reel 20.
Is detected as the rotation amount.

When the tongue is attached to the buckle and the buckle switch 122 is turned on, the ultrasonic motor 24 rotates the spring case 34 a predetermined number of times in the direction of tightening the spring 32 to increase the winding force of the spring 32.

As a result, the slack of the seat belt 18 is removed, and the seat belt 18 fits perfectly to the occupant.

In this state, there is a strong sense of pressure on the occupants,
Next, the spring case 34 is driven by the ultrasonic motor 24.
Is rotated a predetermined number of times in the direction in which the spring 32 is loosened.
Thereby, the feeling of pressure on the seat belt 18 is reduced or eliminated.

When the buckle switch 122 is turned off, the ultrasonic motor 24 rotates the spring case 34 in the direction in which the spring 32 is tightened. Thereby, the reel 20 rotates strongly and rapidly, and the seat belt 18 is rapidly wound up.

FIG. 5 is a correlation diagram between the torque applied to the reel 20 by the spring 32 used in this embodiment and the rotation amount of the spring case 34, and the horizontal axis represents the rotation amount of the spring case 34 (unit). : Number of times), and the vertical axis indicates torque.

As described above, the spring 32 is connected to the inner peripheral side 32.
a has a higher spring constant than the outer peripheral side 32b. When the spring case 34 you turn the seat belt winding direction (A ₂ direction), although initially tightened weak portion of the spring 32 (32 b) is wound, the torque is not significantly increased even if progress is tight winding at this time .

When the spring case 34 rotates about nine times, the strong portion (32a) of the spring 32 thereafter
Is also tightened, and the torque rapidly increases with an increase in the amount of rotation of the spring case 34. If the rotation amount of the spring case 34 exceeds 12 times, the strong portion 32
Since the tightening of a becomes complete, the increase in the torque becomes slow. When the spring case 34 rotates about 26 times, the whole of the spring 32 is tightly wound, and the torque increases extremely sharply with the rotation of the spring case 34.

In this embodiment, when the seat belt 18 is stored in the retractor, a relatively high torque near the zone B in FIG. 5 is applied to prevent the tongs from coming out by its own weight. the spring case 32 so as to obtain keep a state of being rotated about 10-11 times the a ₂ direction. That is, keep the ultrasonic motor 24 as detected rotation amount of the rotary encoder 37 is about 11 turns from 10 rotates in the A ₂ direction and then is stopped in this state.

When the occupant starts to pull out the seat belt 18, the rotary encoder 107 on the reel 20 detects that the seat belt has been pulled out. Therefore, the ultrasonic motor 24
The rotated about 3-5 turns A ₁ direction, torque is made to be weak in the vicinity A zone of Figure 5. This allows the occupant to pull out the seat belt 18 lightly and smoothly.

[0062] After pulling out the seat belt 18, the engagement of the tongue into the buckle, the ultrasonic motor 24 so that the torque is near B zone rotates the spring 32 to the A ₂ direction, the tension of the seat belt 18 Raising the seat belt 18 removes the slack, and fits the seat belt 18 to the occupant. Once holding torque to B zone, is again rotating the ultrasonic motor 24 is spring 32 so that the torque becomes A zone A ₁ direction.

[0063] Then, when the tongue from the buckle is dissociated, the ultrasonic motor 24 so that the torque becomes the C zone rotates the spring case 34 in the A ₂ direction. Thereby, the seat belt 18 is strongly and quickly wound up.
When the rotation amount of the reel 20 detected by the rotary encoder 107 becomes a value indicating the completion of the seat belt winding,
Torque ultrasonic motor 24 so that the B zone rotates the spring case 34 in A ₁ direction.

In the above embodiment, the frame 10
The pawl 58 is pivotally supported on the reel 20 and the pawl 58 is engaged with the ratchet wheel 38 provided on the reel 20. In the present invention, the pawl 58 is pivotally supported on the reel 20 side and the ratchet is provided on the inner peripheral surface of the hole 28. Teeth may be provided so that the pawl engages the ratchet teeth.

[0065]

As described above, according to the present invention, the seat belt can be pulled out lightly when the seat belt is pulled out, and when the seat belt is worn, the seat belt fits perfectly to the occupant, and the feeling of pressure on the occupant is reduced or eliminated. Then, when the tongue is released from the buckle, the seat belt can be powerfully and quickly wound up.

In the present invention, since the spring case is rotated by the high-torque ultrasonic motor, a speed reduction mechanism such as a gear train is not required, and the operating noise during rotation of the spring case is extremely small. Further, since the stop torque when the power is not supplied to the ultrasonic motor is large, an extra stopper mechanism for stopping the spring case is unnecessary. It should be noted that, even if the ultrasonic motor fails to rotate for some reason, the seat belt can be pulled out and worn.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a seat belt retractor according to the present invention.

FIG. 2 is an enlarged view of the lock mechanism of FIG.

FIG. 3 is a perspective view of a seat belt retractor according to the present invention.

FIG. 4 is a sectional view of a seat belt retractor according to the present invention.

FIG. 5 is a characteristic diagram of a mainspring used in the present invention.

FIG. 6 is a control block diagram according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Frame 12,14 Side wall part 20 Reel 24 Ultrasonic motor 26 Spring mechanism 30 Second reel shaft 31 Second reel shaft 32 Spring 33 Housing 34 Spring case 34c Case shaft 36 Shaft hole 37 Rotary encoder 40 First reel shaft 42 tie plate 44 lock ring 58 pawl 66 overhang portion 72 hook retainer 74 hook 76,78 projection 80,82 hole 90 gear ring 104 convex 107 rotary encoder 110 piezoelectric element row 112 annular stator

Claims (6)

[Claims] 1. A reel for winding a seat belt, one end connected to the reel, a spring urging the reel in a seat belt winding direction, and the other end of the spring being connected. A movable member that can move in a direction to change the biasing force of the spring; an ultrasonic motor that changes the biasing force by moving the movable member; and a biasing force detection unit that detects a biasing force generated by the spring; A biasing force control unit that controls the biasing force by moving the movable member by the ultrasonic motor so that the biasing force detected by the biasing force detection unit becomes a target value. 2. The seat belt retractor according to claim 1, wherein the spring is a spiral spring having at least two portions having different spring constants in a spiral direction. 3. The reel according to claim 1, wherein the movable member is a spring case surrounding a spring, and the spring case is rotatable around an axis of the reel. Seat belt retractor. 4. An apparatus according to claim 3, wherein said urging force detecting means includes means for detecting a rotation amount of said reel, means for detecting a rotation amount of said spring case, and a difference between the detected rotation amounts. Means for calculating an urging force. 5. The reel according to claim 4, wherein a frame having a pair of parallel side walls and a connecting portion connecting the side walls is connected to the side of the axis of the reel. And a first reel shaft protruding from an axial center position of one end face of the reel is provided with an emergency locking mechanism for a seat belt retractor. The reel rotation amount detecting means is connected, and the spring is wound around the outer periphery of a second reel shaft protruding from the axial position of the other end surface of the reel. A case shaft protrudes out of the frame coaxially with the core, and the case shaft is located at the rotor axis position of the ultrasonic motor arranged outside the spring case. A seat belt retractor having a shaft hole in which a shaft is fitted, and wherein the case rotation amount detecting means disposed outside the ultrasonic motor is connected to a tip of the case shaft. 6. The device according to claim 4, further comprising tongue engagement detecting means for detecting that the tongue has engaged with the buckle, wherein the urging force control means includes a spring for retracting the seatbelt. the biasing force as T _1, after the seat belt withdrawing, the urging force of the spring until tongue engages the buckle T
₁ and small T ₂ than, after the tongue is engaged with the buckle, once the urging force of the spring and higher T ₃ than T _2, then the biasing force and low T ₄ than T _3, tongue buckle Is disengaged.
Seat to the belt storage completion, the seat belt retractor, characterized in that the biasing force higher T ₅ than either T ₁ and T _3.